Two decades have elapsed since the publication of the earliest study from this clinic 13 concerning arteriovenous aneurysms. Although numerous communications, 36-40 have elaborated on our subsequent experiences with this lesion, it would appear justified and profitable at this time to further review the material and assess the results. Moreover, we shall attempt in this monograph to concentrate primarily upon our own clinical material, the largest series published to date, rather than prepare an exhaustive survey 63 of the literature. Attention is invited to the study of TÖNNlS and LANGE-COSACK, with which this series may be collated. Acknowledgements are herein made to other members of the clinic who have previously reported on this subject, from whose studies we have in several instances reproduced case histories. We express our thanks for the assistance rendered by Professor E. LlNDGREN. Drs. H. NORDENSTAM and O. HÖÖK were kind enough to place their services and advice at our disposal. To the Springer Publishing Company goes the gratitude of the authors for the interest, effort and cooperation attending the publication of this monograph.